Google announced plans to gradually remove the option of installing Chrome extensions from a remote website. Google says this interaction pattern has been abused by extension developers, who often used inline installation to distribute malicious Chrome extensions. Starting September 12, 2018, inline installation will be disabled for existing extensions, and users will be automatically redirected to the Chrome Web Store to complete the installation. In early December 2018, the inline install API method will be removed from Chrome 71. The phase-out process will take place in three stages, detailed below.
Source: https://www.bleepingcomputer.com/news/google/google-removes-the-option-of-installing-chrome-extensions-via-remote-sites/